Batteries such as lithium-ion batteries are a common source of electrical energy for mobile phones, tablet and laptop computers, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), industrial equipment such as forklifts and robots, stationary power generators such as solar power generators and wind power generators, as well as other applications. A lithium-ion battery in these types of applications typically includes a battery pack made up of numerous individual battery cells—sometimes hundreds or thousands of cells. During use, the charging and discharging performance and the life of the batteries can degrade appreciably due to rising internal core temperatures of the battery cells. In some cases, lithium-ion batteries have been shown to exhibit a somewhat confined window of temperatures in which they can effectively perform (e.g., −10° C. to 50° C.). Accordingly, attempts have been made to monitor the internal core temperatures of battery cells in order to better manage cooling systems of the battery pack and hence the temperatures of the batteries.
Past attempts, however, have been fraught with shortcomings and can be largely inaccurate, unreliable, and in some cases impractical. In one example, a surface temperature of a battery cell is measured and taken as its core temperature. But this can be grossly inaccurate as temperatures between the surface and the core can differ by as much as 30° C. In another example, temperature sensors are installed inside of a battery cell's internal core to take temperature measurements at the core. But this can be impractical due to the accompanying cost for equipping the hundreds or even thousands of battery cells often found in the types of applications mentioned above.